The present invention generally relates to color video signal recording and/or reproducing systems, and more particularly to a system for recording and/or reproducing a color video signal so that a high-quality reproduced color picture can be obtained even in a system in which the color video signal is recorded in a manner such that positions on a recording medium where the horizontal synchronizing signals of the color video signal are recorded are not aligned in mutually adjacent tracks which are contiguously formed on the recording medium without a guard band between the mutually adjacent tracks.
Generally, in the recording system of a SECAM system color video signal recording and/or reproducing system, for example, a SECAM system color video signal is supplied to a lowpass filter and a bandpass filter, and a luminance signal is separated and filtered in the lowpass filter while a carrier chrominance signal is separated and filtered in the bandpass filter. As is well known, the above carrier chrominance signal is a signal in which a first frequency modulated signal which is obtained by frequency-modulating a first chrominance subcarrier by a color difference signal B-Y, and a second frequency modulated signal which is obtained by frequency modulating a second chrominance subcarrier by a color difference signal R-Y, are time-sequentially multiplexed in an alternate manner for every one horizontal scanning period (1H). The above carrier chrominance signal having a carrier frequency of 3.9 MHz to 4.75 MHz, for example, is supplied to a frequency dividing circuit wherein the carrier chrominance signal is frequency-divided and converted into a low frequency range. Moreover, the carrier frequency of the carrier chrominance signal is set to a frequency in a range of 0.97 MHz to 1.19 MHz, for example, and the frequency deviation width is reduced. The carrier chrominance signal which is converted into the low frequency range and the frequency modulated luminance signal, are subjected to a frequency-division-multiplexing and then amplified to be formed into a composite color video signal. This composite color video signal is supplied to a pair of magnetic heads having gaps of mutually different azimuth angles.
On the other hand, in the reproducing system, the pair of magnetic heads alternately reproduce the composite color video signal which is recorded on the magnetic recording medium (magnetic tape). The outputs of the pair of magnetic heads are respectively amplified, and are formed into a continuous signal by being switched alternately in a switching circuit. The frequency modulated luminance signal in this continuous signal, is separated and filtered in a highpass filter, and is then demodulated and converted into the luminance signal in a demodulating circuit. The frequency converted carrier chrominance signal in the continuous signal, is separated and filtered in a lowpass filter, and is then supplied to a multiplying circuit wherein the carrier frequency is restored into the original carrier frequency. The output of this multiplying circuit is supplied to a bandpass filter so as to obtain a predetermined frequency band. The reproduced carrier chrominance signal and the reproduced luminance signal from the demodulating circuit, are multiplexed and formed into a reproduced SECAM system color video signal in a multiplexing circuit.
As one example of a track pattern formed on the magnetic tape according to the above described recording and/or reproducing system, there is a track pattern in which mutually adjacent tracks are formed on the magnetic tape without a guard band formed between the adjacent tracks, by use of a pair of magnetic heads having gaps of mutually different azimuth angles. In this type of a track pattern, the positions where the horizontal synchronizing signals are recorded in the adjacent tracks, are arranged to be in alignment along a direction perpendicular to the longitudinal direction of the track, for example. This alignment of the positions where the horizontal synchronizing signals are recorded, is sometimes referred to as an H-alignment. In addition, the frequency modulated signal components of the carrier chrominance signal which is recorded after being frequency converted into the low frequency range, are the same at a certain recorded section in which the frequency converted carrier chrominance signal is recorded and the color difference signal R-Y is frequency modulated, and at a section of an adjacent track which is adjacent to the certain recorded section. Accordingly, very little crosstalk is introduced between the adjacent tracks by the carrier chrominance signal in the low frequency range, and the demodulated color video signal is hardly affected by the crosstalk.
It is sometimes desirable to carry out recording and/or reproduction of a long duration. When carrying out such a long-duration recording and/or reproduction in a magnetic recording and/or reproducing apparatus which forms the track pattern described heretofore, only the tape traveling speed is reduced. That is, the diameter of the drum which carries the magnetic heads, the tape width, the rotational speed of the drum, and the number of horizontal scanning lines all remain unchanged. When carrying out four hours of recording and/or reproduction by use of a magnetic tape which is designed for two hours of recording and/or reproduction, for example, only the tape traveling speed is reduced to 1/2 the tape traveling speed which would otherwise be used for two hours of recording and/or reproduction with such a magnetic tape. In the track pattern obtained when four hours of recording and/or reproduction is carried out by use of the magnetic tape which is designed for two hours of recording and/or reproduction, the positions where the horizontal synchronizing signals are recorded are not in alignment in the mutually adjacent tracks. Accordingly, no correlation exists between the adjacent tracks, and the carrier frequencies of the carrier chrominance signal in the low frequency range differ in the adjacent tracks. In this case, because the adjacent tracks are recorded by the magnetic heads having gaps of mutually different azimuth angles, the azimuth loss of the frequency modulated luminance signal becomes large in the high frequency range. As a result, with respect to the frequency modulated luminance signal, there is little effect of crosstalk from the adjacent tracks. However, the azimuth loss of the recorded carrier chrominance signal is small because the recorded carrier chrominance signal is in the low frequency range. Moreover, the effect of crosstalk from the adjacent tracks is large with respect to the carrier chrominance signal, since the carrier frequencies of the recorded carrier chrominance signal differ in the adjacent tracks. Thus, beat interference is introduced.